1. Field of the Invention
This invention relates to a busbar having a C-shaped cross section for busbar trunking systems, switching equipment and the like. Such busbars are used in particular in a busbar system in power distribution equipment and are preferably oriented parallel to one another in a plane by means of rail fasteners.
2. Background Information
Conventional busbars have a solid rectangular cross section, and are fastened parallel to one another at intervals defined by the physical conditions. The busbars are not only subjected to extreme temperature influences, but are also subjected to high mechanical stresses whenever short circuits occur.
In alternating current and three-phase current systems, magnetic fields around the busbars are built up when current flows. These magnetic fields lead to a higher current density in the peripheral regions of the busbars.
In direct-current equipment, the number of busbars connected in parallel can be almost unlimited. However, with alternating current and three-phase current the external rails carry a greater load on account of the current displacement or skin effect. Therefore, as a rule, a maximum of four busbars are connected in parallel and, in order to maintain a more uniform current distribution, the distance between the two innermost busbars is increased, or in other words, the distance between the two innermost busbars is greater than the distance between any one outermost busbar and its adjacent innermost busbar.
The prior art includes busbars having a C-shaped cross section with walls of uniform thickness, whereby the C-shaped profile was designed for the fastening of terminals to the busbar by means of suitable terminal shoes or fastening devices.
In busbar systems in which the conductor busbars are installed in a common plane vertically or horizontally parallel to one another, and the open distance between main conductors is less than 0.8 times the average center-to-center distance between main conductors, the negative influence of the skin effect is more noticeable.